全文获取类型
收费全文 | 5977篇 |
免费 | 275篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 53篇 |
综合类 | 22篇 |
化学工业 | 1100篇 |
金属工艺 | 137篇 |
机械仪表 | 125篇 |
建筑科学 | 296篇 |
矿业工程 | 10篇 |
能源动力 | 229篇 |
轻工业 | 383篇 |
水利工程 | 55篇 |
石油天然气 | 46篇 |
无线电 | 522篇 |
一般工业技术 | 1245篇 |
冶金工业 | 907篇 |
原子能技术 | 51篇 |
自动化技术 | 1092篇 |
出版年
2023年 | 52篇 |
2022年 | 45篇 |
2021年 | 185篇 |
2020年 | 131篇 |
2019年 | 177篇 |
2018年 | 211篇 |
2017年 | 136篇 |
2016年 | 170篇 |
2015年 | 135篇 |
2014年 | 197篇 |
2013年 | 357篇 |
2012年 | 309篇 |
2011年 | 354篇 |
2010年 | 255篇 |
2009年 | 265篇 |
2008年 | 275篇 |
2007年 | 275篇 |
2006年 | 204篇 |
2005年 | 195篇 |
2004年 | 169篇 |
2003年 | 170篇 |
2002年 | 146篇 |
2001年 | 88篇 |
2000年 | 99篇 |
1999年 | 74篇 |
1998年 | 245篇 |
1997年 | 159篇 |
1996年 | 97篇 |
1995年 | 113篇 |
1994年 | 80篇 |
1993年 | 78篇 |
1992年 | 64篇 |
1991年 | 56篇 |
1990年 | 40篇 |
1989年 | 38篇 |
1988年 | 47篇 |
1987年 | 37篇 |
1986年 | 31篇 |
1985年 | 39篇 |
1984年 | 28篇 |
1983年 | 25篇 |
1982年 | 38篇 |
1981年 | 39篇 |
1980年 | 31篇 |
1979年 | 34篇 |
1978年 | 35篇 |
1977年 | 37篇 |
1976年 | 54篇 |
1975年 | 19篇 |
1972年 | 17篇 |
排序方式: 共有6273条查询结果,搜索用时 359 毫秒
71.
In some multiple treatment arm clinical trials there is an order of preference for the treatments based on secondary considerations like toxicity or cost. In this paper, we consider the case where two or more treatments could have equal prior preference. This formulation includes the problem of comparing several equally preferred experimental treatments to one control, or the comparison of a combination with its components. Our decision procedures will guarantee a high selection probability for the correct treatment(s) when that selection is appropriate. We establish sample size requirements for our decision procedures which can be applied to clinical trials with normal, binomial, or right censored exponential endpoints. 相似文献
72.
In a prospective open study we investigated Chlamydia pneumoniae infections in 36 consecutively admitted patients: 26 males, mean age 53.4 yr, range 36-70 yr, 10 females mean age 57.7 yr, range 47-70 yr, suffering myocardial infarction (24 acute, 2 previous) or angina pectoris (10). Antibody serum levels were measured by the immunefluorescent method and they were as follows: negative 5, low 12, medium/high 11, chronic infection 5, recent infection 3. The 3 cases considered as recent infections are described in detail. 相似文献
73.
The β and γ decay of uranium atoms from xUO3(100 - x)[3B2O3 · MO] glass systems, where M=Sr or Pb and 0 ≤ × ≤ 20 mol%, is investigated. The γ decay data are very close to each other, for the same UO3 contents, in both the systems. The composition dependence of the β decay exhibits a lower slope in the lead borate matrix than in the strontium borate matrix. The ratio between the β activity of samples with the same uranium ion concentrations in the two investigated glass systems is a function of the x values. The results are correlated with the amount of radioactive nuclides and with the structural environments of the radionuclides. The leaching treatment in water at temperatures below 100°C evidenced no aqueous dissolution of glass samples. 相似文献
74.
Koch David Despotovic Miroslav Thaler Simon Zeppelzauer Matthias 《Applied Intelligence》2021,51(11):8106-8106
Applied Intelligence - A Correction to this paper has been published: https://doi.org/10.1007/s10489-021-02433-z 相似文献
75.
Jantsch Simon Müller David Baier Christel Klein Joachim 《Formal Methods in System Design》2021,58(1-2):42-82
Formal Methods in System Design - Due to the high complexity of translating linear temporal logic (LTL) to deterministic automata, several forms of “restricted” nondeterminism have been... 相似文献
76.
C. Christopher ColumbusAuthor Vitae K. Chandrasekaran Author VitaeSishaj P. Simon Author Vitae 《Applied Soft Computing》2012,12(1):145-160
This paper proposes a nodal ant colony optimization (NACO) technique to solve profit based unit commitment problem (PBUCP). Generation companies (GENCOs) in a competitive restructured power market, schedule their generators with an objective to maximize their own profit without any regard for system social benefit. Power and reserve prices become important factors in decision process. Ant colony optimization that mimics the behavior of ants foraging activities is suitably implemented to search the UCP search space. Here a search space consisting of optimal combination of binary nodes for unit ON/OFF status is represented for the movement of the ants to maintain good exploration and exploitation search capabilities. The proposed model help GENCOs to make decisions on the quantity of power and reserve that must be put up for sale in the markets and also to schedule generators in order to receive the maximum profit. The effectiveness of the proposed technique for PBUCP is validated on 10 and 36 generating unit systems available in the literature. NACO yields an increase of profit, greater than 1.5%, in comparison with the basic ACO, Muller method and hybrid LR-GA. 相似文献
77.
Conclusion The dislocation structure and the microstructure of diffusion layers, which at the temperature of diffusion annealing represent a single-phase solid solution of boron in -iron, are determined by the local boron concentration and by the cooling rate from the austenitic state. The high dislocation density in the layer, which is found independently of the cooling rate, testifies to the fact that diffusion of boron in iron is accompanied by the formation of a large number of dislocations. The presence of boron in the solution slows down their redistribution and annihilation in the porcess of high-temperature annealing.The distribution of microdistortions across the thickness of the layer is characterized by the existence of a maximum near the diffusion line; this is due to the high density of the randomly distributed dislocations on the boundary between the diffusion zone and iron.Tula Polytechnic Institute. Translated from Metallovedenie i Termicheskaya obrabotka Metallov, No. 1, pp. 20–23, January, 1988. 相似文献
78.
Wollaston prism with large split angle 总被引:1,自引:0,他引:1
Simon MC 《Applied optics》1986,25(3):369-376
The image formation through a Wollaston prism with large split angle is studied. Formulas for the split angle, approximate calculations of aberrations, and ray tracings are used. The most important aberrations found are astigmatism and anamorphic distortion. Tilting the Wollaston with respect to the incident beam may reduce these aberrations, and if the orientation of the optical axis in the first element is varied it is possible to cancel one of the two aberrations for both images simultaneously, while the other one is substantially reduced. With an adequate adjustment of all the construction parameters the images become sharp enough to allow the use of large split angles (approximately 15 degrees). 相似文献
79.
80.